Wire wound resistor



May 19, 1964 A. HAYNMAN 3,134,087

WIRE WOUND RESISTOR Filed March 16, 1961 M 1 1 1 z I, I, 1 I I 14 1 1 11 I l I, I:

INVENTOR. ALEXANDRE HAYNMAN ATTORNEY United States Patent 3,134,087 WIREWOUND RESISTOR Alexandre Haynman, Copenhagen-Vanlose, Denmark,

assignor to International Resistance Company, Philadelphia, Pa. s

Filed Mar. 16, 1961, Ser. No. 96,260 3 Claims. (Cl. 338332) The presentinvention relates to a wire wound resistor, and more particularly to awire wound resistor sealed in a casing.

It is common practice to enclose an electrical resistor in a jacket orcasing of an insulating material. Such a jacket or casing serves toelectrically insulate the resistor, and to protect the resistor frommoisture and dirt which can adversely affect the electricalcharacteristics of the resistor. One manner of so protecting anelectrical resistor is to place the resistance element in a tubularsleeve of an electrical insulating material, and to seal the ends of thesleeve. However, a problem with such enclosed resistors is the manner ofmaking electrical connection to the resistance element within thesleeve.

One method of making electrical connection to the electrical resistanceelement in the sleeve is to attach terminal wires to the resistanceelement, which terminal wires project through the sealed ends of thesleeve. However, the attachment of the terminal wires to the resistanceelement, and the providing of good seals around the terminal wires wherethey project from the sleeve are time consuming operations whichincrease the cost of the resistor. Another method of making electricalconnections to the resistance element is to seal the ends of the sleevewith metal caps, and electrically connect the resistance element to theinner surfaces of the caps. However, the connection of the resistanceelement to the metal caps is a difficult task, particularly when theresistance element is a fine wire.

It is an object of the present invention to provide a novel wire woundelectrical resistor.

It is another object of the present invention to provide a novel wirewound electrical resistor sealed in an insulating casing.

It is a further object of the present invention to provide a wire woundelectrical resistor sealed in an insulating casing which is easy toassemble so as to be inexpensive.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in thedrawing a form which is presently preferred; it being understood,however, that this invention is not limited to theprecise arrangementsand instrumentalities shown.

The drawing is a sectional view of the wire wound resistor of thepresent invention partially in elevation, and with a portion of thewinding broken away.

Referring to the drawing, the resistor of the present invention isgenerally designated as 10.

Resistor comprises a resistance element 12 disposed within a tubularsleeve 14 of an electrical insulating material, such as a ceramic orplastic. Resistance element 12 comprises a core 16 of an electricalinsulating material, such as a ceramic, plastic, or a heavy fibrouscord. A resistance wire 18 is helically wound around the core 16 alongthe entire length of the core. The resistance wire 18 may be as fine as0.001 inch in diameter. The diameter, composition, and length of theresistance wire 18 determines the resistance value of the resistor 10.The end portions 18a and 18b of the resistance wire 18 are left free toextend beyond the ends of the core 16.

With the resistance element 12 disposed within the sleeve 14, the freeends 18a and 18b of the resistance wire 18 are pulled from the ends ofthe sleeve. Each of the free ends 18a and 18b of the resistance wire 18is disposed Patented May 19, .1964

across the adjacent end of the sleeve 14, and then longitudinally alongthe outer surface of the sleeve 14 toward the other end of the sleeve. Aseparate cap 20 of an electrically conductive metal is placed on eachend of the sleeve 14.

Each of the caps 20 has a bottom 22 which extends transversely acrossthe entire end of the sleeve 14, and a tubular rim 24 which fits tightlyaround the outer surface of the sleeve 14. Thus, the caps 20 sealinglyclose the ends of the sleeve 14. In addition, as the caps 20 are placedon the ends of the sleeve 14, the rims 24 of the caps 20 slide over andengage the free ends 18a and 18b of the resistance wire 18. Thus, thecaps 20 provide the electrical connections to the ends of the resistancewire 18. Since the resistance wire 18 is a very fine wire, the free ends18a and 18b which extend between the rims 24 of the caps 20 and theouter surface of the sleeve 14, do not interfere with the tight fitbetween the caps 20 and the sleeve 14. It has been found that when thecaps 20 are placed on the ends of the sleeve 14, the sliding engagementbetween the rims 24 of the caps 20 and the ends 18a and 18b of theresistance Wire 18 does not break the resistance wire even though theresistance wire is a very fine wire.

To assemble the wire wound resistor 10 of the present invention, it isonly necessary to insert the resistance element 12 into the sleeve 14.The free end 18a of the resistance wire 18 is then pulled across theouter surface of the sleeve 14, and the cap 20 is then forced onto andaround the end of the sleeve 14 and over the free end 18a of theresistance wire. The other free end 18b of the resistance wire 18 isthen placed across the outer surface of the sleeve 14, and the other cap20 forced on the end of the sleeve 14 and over the free end 181) of theresistance wire. Thus, the wire wound resistor 10 of the presentinvention is assembled quickly and easily so that the resistor 10 isinexpensive to manufacture.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specifications as indicating the scope of theinvention.

I claim:

1. A wire wound resistor comprising a hollow sleeve of an electricalinsulating material, a resistance element within said sleeve, saidresistance element including a helically wound resistance wire, each ofthe free ends of said wire extending from a separate end of said sleeveand over the outer surface of the sleeve, and a separate cap of anelectrically conductive metal fitting over each end of said sleeve, eachof said caps extending over and directly electrically contacting a freeend of said resistance wire.

2. A wire wound resistor comprising a hollow sleeve of an electricalinsulating material, a resistance element within said sleeve, saidresistance element including a helically wound resistance wire, each ofthe free ends of said wire extending from a separate end of said sleeveand over the outer surface of the sleeve, and a separate cap of anelectrically conductive metal fitting over each end of said sleeve, eachof said caps having a bottom extending transversely across an end ofsaid sleeve and a tubular rim extending around and tightly engaging theouter surface of the sleeve, the rim of each of said caps extending overand directly electrically contacting a free end of said resistance wire.

3. A wire wound resistor comprising a hollow sleeve of an electricalinsulating material, a resistance element within said sleeve, saidresistance element including a core of an electrical insulating materialand a resistance wire helically wound around and along said core withthe free ends 4 of said wire extending beyond the ends of the core, eachReferences Cited in the file of this patent of the free ends of saidwire extending from a separate UNITED STATES PATENTS end of said sleeveand over the outer surface of the sleeve, and a separate cap of anelectrically conductive metal 1,208,756 Khotinsky Dec. 19, 1916 fittingover each end of said sleeve, each of said caps 5 1,576,165 W i e Mar.9, 1926 having a bottom extending transversely across an end of1,608,005 schoeppler 1926 said sleeve and a tubular rim extending aroundand tightly 1,910,866 Van Nostrand May 23, 1933 engaging the outersurface of the sleeve, the rim of each 2,332,255 P OISkY Oct. 19, 1943of said caps extending over and directly electrically con- ,677,118Stone Apr. 27, 1954 tacting a free end of said resistance wire. 102,680,173 Hitchcock June 1, 1954

1. A WIRE WOUND RESISTOR COMPRISING A HOLLOW SLEEVE OF AN ELECTRICAL INSULATING MATEIRAL, A RESISTANCE ELEMENT WITHIN SAID SLEEVE, SAID RESISTANCE-ELEMENT INCLUDING A HELICALLY WOUND RESISTANCE WIRE, EACH OF THE FREE ENDS OF SAID WIRE EXTENDING FROM A SEPARATE END OF SAID SLEEVE AND OVER THE OUTER SURFACE OF THE SLEEVE, AND A SEPARATE CAP OF AN ELECTRICALLY CONDUCTIVE METAL FITTING OVER EACH END OF SAID SLEEVE, EACH OF SAID CAPS EXTENDING OVER AND DIRECTLY ELECTRICALLY CONTACTING A FREE END OF SAID RESISTANCE WIRE. 